BACKGROUND NARRATIVES

Project Summary: The goal of this USGS project
is to document decade- to century-
scale processes associated with sediment transport in Florida Bay. The results will
quantify the influence of bottom topography on water quality in the Bay so that sea level
and bathymetric change can be integrated with numerical modeling efforts conducted by
cooperating agencies.

Project Justification: Recent algal blooms and
seagrass mortality have raised
concerns about the water quality of Florida Bay, particularly its nutrient content (nitrogen
and phosphorous), hypersalinity, and turbidity. Water quality is closely tied to sediment
accumulation because mudbanks severely limit circulation in the bay. Over decades to
centuries, bathymetric changes due to erosion or sedimentation affect water circulation and
hypersalinity. The impact on circulation depends on the interplay between sediment
accumulation and sea-level rise. Management agencies are planning a "restoration" of
Florida Bay that centers around increasing the amount of fresh water entering the estuary.
In order to predict the results of various restoration alternatives, long-term changes in the
bathymetry and volumetrics of the bay must be Incorporated in hydrodynamic models being
constructed by other agencies.

Project Objectives:Five interrelated activities are
underway for this project: 1) core
analyses; 2) local sediment elevation surveys; 3) mudbank profiling and surveys; 4)
integration of sedimentary analyses with circulation patterns and sea-level history; and 5)
salinity surveys to document effects of mudbanks on circulation;. This project integrates
results from several other ongoing and new projects in the USGS Ecosystem program and
other programs. In particular, the bathymetry, turbidity, sediment transport, lead-2 10
dating, and ecosystem history projects in the bay both use results from this project and
provide information to the project. Additional complimentary information is being provided
by the Marine and Coastal Program project "Sedimentation and water quality in Florida
Bay" that provides funding for determining past salinity from geochemical analyses of
fossil mollusks as part of a cooperative with the South Florida Water Management District.
It is a goal of the work proposed here to integrate these various projects into a sediment
budget for Florida Bay

Overall Strategy, Study Design, and Planned Major Products:
Four of five activities are designed to provide measures of
sedimentation or erosion on mudbanks, the fifth activity documents the influence of
mudbanks on water salinity.
1) Coring: Cores taken for this and other projects have been x-rayed and some
provide measurable sections of sediment above known (dated) horizons. These provide an
average sedimentation rate based on the age of the horizon.
2) Pb-210 dating: A few cores are suitable for lead-210 dating from which an
average sedimentation rate can be calculated. The lead-210 method has the advantage of
providing a continuous record of sedimentation rates during the last century with a
resolution of a few years. However, there are only a few sites in the Bay that are suitable
for analyses.
3) Sedimentation site monitoring: Fifteen local sediment survey stations have
been established in the bay. These are driven to bedrock and provide platforms for
seasonal sediment elevation measurements accurate to a few millimeters. Five are in the
eastern bay, five in the central bay, and five in the western bay.
4) Bank profiles: Each group of five survey stations is arranged in a transact
across a mudbank. Repeated precision profiling across each mudbank will provide a multi-
year record of sediment erosion or accretion on the bank and allow the data from individual
survey stations, cores, and marker horizon sites to be placed in context of bank-wide
patterns. Sedimentation rates provide basic data for determining long-term
accumulation/erosion patterns and subsequent volume changes in the bay as a result of sea-
level rise.
5) Salinity surveys: Salinity maps, produced semi monthly, illustrate the
influence of mudbanks on circulation. The contours of salinity, constructed from bay-wide
surveys, show conformity with the banks and often coincide with the banks. Turbid and
algal bloom regions, monitored by other agencies, are also confined by shallow banks.
Three measures of water quality (salinity, turbidity and chlorophyll) indicate that the
mudbanks are a dominant control on circulation. Understanding mudbank dynamics is
critical to predicting future water quality of the Bay.

WORK PLAN

Overall:During FY 1998 data will be collected from all the
stations and dating work will
continue on sediment cores. The establishment of elevations of NPS tide gauges (during
late FY1997 and early FY1998) allows the placement of bank transects on a geoid reference
frame relative to sea level. During FY 1998 sea-level and elevation data will be processed
so that, for the first time, exposure indices of mudbanks can be calculated, providing
quantitative measures of bank flooding and drying. Sediment production rates will be
refined by measuring the carbon-14 activity of core intervals already dated by the lead-2 10
method in order to determine how much sediment has been produced during the past 35
years (using carbon-14 produced during atmospheric nuclear testing as a tracer). During
FY 1998 initial synthesis of production , sedimentation and erosion rates, will begin in
anticipation of completion in FY 1999. During FY1999, results from a sediment transport
model, will allow development of a sediment budget for the bay.

Timeline: Regular (semimonthly) meetings are planned
with clients through committee and group
activities and as required by our cooperative agreement. Field work is planned
for four weeks each
summer, in two two-week sessions (July and August), and two weeks at the end of the wet season
and two weeks at the end of the dry season. Field work is subject to delay or extension pending
weather, furloughs, availability of boats and vehicles, etc. Product completion is described in next
section. This project also supports USGS and interagency administrative activities
associated with
the Task Force for South Florida Ecosystem Restoration, in particular the steering committee,
theme coordinator activities in the USGS, as well as interagency Science Subgroup and Florida
Bay Program Management Committee activities.

Planned Deliverables/Products: Analyses cores from three mudbanks
will be summarized in a
manuscript for a special volume of Estuaries dedicated to long-term change in Florida Bay. A
final
report will detail initial results and results from duplicate cores at project end. Each year
presentations are prepared for the USGS South Florida Program Meeting, the Florida Bay Science
Conference, and a national scientific society meeting, either GSA, AGU or SEPM. Presentations
are prepared for client workshops (SFWMS, ACOE, NOAA, and NPS). Often these meetings are
unknown in time for workplans, For example, on May 10th the ACOE has invited the USGS to a
workshop "Modeling Sediment Resuspension, Water Quality And Aquatic Vegetation" in New
Orleans, June 24-25, 1997. This is the third unscheduled client workshop this FY. A presentation
will be prepares for the annual USGS program meeting. Abstracts will be written, reviewed and
approved for all meetings that require formal presentations. One journal manuscript will be
prepared. Semimonthly salinity maps of Florida Bay will continue to be produced. All results are
posted on the internet or presented at science meetings. Results are conveyed to management at
managers meetings, through workplans, proposals, and reports.

Planned Outreach Activities: During FY 1998 client
requirements will continue to be met through continued regular client
meetings, through direction from the Florida Bay Interagency Science Program Management
Council, and through continued interaction with collaborators and clients listed above
in the first section.

Prior Accomplishments in Proposed Area of Work:

New Directions, Expansion of Continuing Project (if applicable):
This project does not anticipate new directions or expansions. It does however support the
principle investigator's time and travel on long range planning for the Florida Bay PMC (see
product #9) and the USGS South Florida Program.

ACCOMPLISHMENTS, OUTCOMES, PRODUCTS, OUTREACH

Accomplishments and Outcomes, Including Outreach:
Successful completion of Phase One of our contract work on Ecosystem History with the South
Florida water management district has led to a renewal of this work during FY1997. My time
constraints have prevented me from taking on the renewal, and the project is now in the capable
hands of Chuck Homes. Continued to serve as GD representative to Program and Florida Bay
Coordinator and represent the USGS on the Interagency Florida Bay Program Management
Council.

NEEDS

Required Expertise: Local knowledge of Florida Bay, carbonate
sedimentology, marine geological field methods, laboratory methods, public speaking,
scientific
writing, report writing, popular writing, drafting, statistics, contracting, budgeting,
planning, sales
techniques, quality control, outreach. It has been particularly difficult to
retain personnel. At the
present moment, however, these problems are solved for the short-term. The difficulties could
return at any moment. The main personnel issue is holding qualified people in temporary
positions. Primary expertise issue is setting of priorities for core capabilities and
operations in St.
Pete office.